[jhb_airlines] Re: Gross Weight

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Sun, 19 Dec 2004 17:38:28 -0000

It is quite easy to overload any aircraft and only close inspection of =
the
load sheet will confirm this. I'm guessing PF have just let it run so =
that
users can learn the hard way.

In truth there isn't any great penalty for overloading an aircraft if =
you
know what you are doing. I once flew a PA28 that was 500lb overweight - =
a
huge amount considering its normal payload was only 750lb. The extra =
weight
increased stall speeds by about 10kts so it was necessary to factor much
higher take off and approach speeds. The only other consideration was an
extremely gentle landing so that the gear didn't suffer any great =
landing
stresses. Wing spar loading was something I was worried about as all the
extra weight was in the fuselage but as it was the Chief Engineer that =
was
with me (and had loaded up the aircraft) I assumed he knew more about =
this
than I did. He did say that full fuel was necessary to keep weight
distribution sensible and that people who put in minimum fuel to counter
more cabin weight were actually making things worse.

The one thing that isn't good is getting the aircraft out of its CG =
range.
In the case above the weight was even across the aircraft (I had a  long
metal bar actually resting on the top of the panel and running the =
length of
the cabin) and the CG was right in the middle of the operational range.
Getting the CG too far forward is tricky in most aircraft (except an =
ATP)
and this isn't too critical unless you run out of control response. =
Getting
the CG aft of max limit is much more dangerous because you not only lose
control effectiveness but you can end up with the Centre of Pressure =
being
near or forward of the wing's aerodynamic centre and this will result in
severe pitch instability (dynamic instability).

With airliners the situation is different because factors become more
critical. Pitch stability and pitch trim are far more sensitive in =
airliners
because most are designed with extremely small tailplane/elevator area. =
This
is done to improve cruise speeds but the downside is that the aircraft
cannot be trimmed by elevator alone as with most light aircraft. Instead =
the
whole tailplane is used for trimming and correct settings are essential. =
If
the tailplane is not set at the correct trim angle then the aircraft =
will
simply fail to take off - or pitch up into a stall. In a light aircraft =
a
mistrimmed aircraft just results in having to heave harder but in an
airliner it is beyond the crew's power to overcome it.

There are one or two aircraft in FS that mimic trim correctly but it is
generally too easy to take off with the wrong settings. If we had proper
force feedback and a stick that was bolted to the desk we could find out
just how hard it can be to pull the stick back against a mis trim force =
-
but that will never happen..

bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of gwinsk@xxxxxxx
Sent: 19 December 2004 12:41
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Gross Weight


Ignore my reply about the button not showing. Re reading I decided one =
of us
is=20
dislecsxtic and reworded the appropriate button gauge input. Now visible =
and
installed. Another check shows it is possible to instal it as a gauge,
rather than as a window.=20
You'd need a fair amount of available panel space, since shrinking it =
makes
the text=20
unreadable. A window, which you can drag wherever it's best seen, is an
acceptable=20
route. Will have a closer look, after returning from lunch with inlaws
visiting the Island,=20
to which I'm being dragged, screaming!
 One of the immediate benefits of this gauge is its overweight warning
display. I've flown=20
the F100 several times and not looked at load, via the menu. Could be it
wouldn't need=20
the Thrust Scalar tweek, if not overloaded. Which does beg the question =
why
they set=20
parrameters that allow the situation, at takeoff...


Gerry Winskill
gwinsk@xxxxxxx




On 19 Dec 2004 at 10:45, Bones wrote:

> OK.
>=20
> Let me play a bit more with it before I send it off. I am now trying=20
> to =3D get it to work with a standard FS icon rather than an on/off=20
> switch and the syntax is slightly different.
>=20
> Are there any other values you would like including whilst I am=20
> working =3D on it? I can ad almost any FS parameter - IAS, TAS, ground =

> speed, empty =3D weight, fuel weight, zero fuel weight etc etc..
>=20
> bones
>=20
> -----Original Message-----
> From: jhb_airlines-bounce@xxxxxxxxxxxxx=20
> [mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of gwinsk@xxxxxxx
> Sent: 18 December 2004 20:15 To: jhb_airlines@xxxxxxxxxxxxx Subject:=20
> [jhb_airlines] Re: Gross Weight
>=20
>=20
> Sorry for the delay. Just finished washing up, after watching the=20
> United match.=3D20 Cowardice in the face of the....oops.  I'm using =
the=20
> Fokker 100, Swissair Tay 620 version, at present.
>=20
> Gerry Winskill
> gwinsk@xxxxxxx
>=20
> On 18 Dec 2004 at 18:36, Bones wrote:
>=20
> > Gerry,
> >=3D20
> > I've been fiddling with XML most of the afternoon and have finally =20
> >got =3D
>=20
> > a readout working. An added bonus is that it can be activated from a =

> > =3D
> =3D3D=3D20
> > switch on the panel. Text size is a bit large but I haven't found =20
> >out=3D20 how to =3D3D reduce this yet. =3D20
> > Can you let me know which aircraft you are thinking of adding this
> > too =3D
>=20
> > =3D3D so I could test it in one? At the moment I have only used it =
on=20
> > =3D
> the=3D20
> > Cessna =3D3D 172.
> >=3D20
> > bones
> >=3D20
> > -----Original Message-----
> > From: jhb_airlines-bounce@xxxxxxxxxxxxx=3D20
> > [mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of =20
> >gwinsk@xxxxxxx Sent: 17 December 2004 21:51 To: =20
> >jhb_airlines@xxxxxxxxxxxxx Subject:=3D20 [jhb_airlines] Re: Gross =20
> >Weight =3D20
> >=3D20
> > I've got the speeds, from the data with the a/c. To pick the
> > relevant=3D20 Vspeed, I need the=3D3D20 AUW; which is the missing =
bit.
> > Another =3D
> approach=3D20
> > would be to use an =3D3D available fuel=3D3D20 gauge, that reports=20
> > current =3D
>=20
> > fuel staus, with wt as an option. Provided =3D3D my checklist=3D3D20 =
=3D
> contains=3D20
> > the wt of a/c + passengers and luggage, without fuel, I could =3D3D=20
> > get =3D
> to=3D20
> > the AUW=3D3D20 just by adding current fuel wt to this wt net of =
fuel.=20
> > =3D
> I'll=3D20
> > try it tomorrow. Incidentally, just finished a flight in the F100.=20
> > It=3D20 cant reach anything like the stated 280=3D3D20 kias climb =
speed=20
> > and is a =3D
>=20
> > bit sluggish down the runway. I'll Power =3D3D Scalar it, tomorrow.=20
> >=3D20  Gerry Winskill
> > gwinsk@xxxxxxx
> >=3D20
> >=3D20
> >=3D20
>=20
>=20
>=20
>=20




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